Adipic acid is a dicarboxylic acidic compound having a molecular formula of (CH2)4(COOH)2. Adipic acid has been widely used as a raw material for nylon resin, plastic plasticizers, and dyes and pharmaceuticals. In particular, as an important intermediate product for the production of a polyamide, such as nylon 6,6, adipic acid has a very high commercial value.
Adipic acid is mainly produced by a chemical method involving a two-step process using a petroleum compound as a raw material. In detail, cyclic compounds, such as phenol, cyclohexane, cyclohexene, and benzene, are used as starting materials and converted to ketone-alcohol oil (KA oil) named cyclohexanone or cyclohexanol. Then, through an oxidation process using nitric acid, adipic acid is produced. Such a chemical process is highly efficient and economical, but use of benzene as a raw material and the production of an enormous amount of nitrogen oxide as a by-product are considered to be problems. In addition to these problems, due to environmental regulations that have recently been strengthened, the need for environmentally friendly processes for the production of adipic acid has emerged. In this regard, efforts to produce adipic acid through microorganisms are about to begin. However, a biosynthesis or biodegradation pathway of 6-aminocaproic acid, which can be used as an intermediate for the production of adipic acid, is not accurately known yet. If a 6-amine group of 6-aminocaproic acid is removed and a ketone group is introduced thereto, adipate semialdehyde is produced, and through an aldehyde dehydrogenase reaction, it is expected that the synthesis of adipic acid is possible (Guerrillot L. et al., Eur J Biochem., 1977, 81(1):185-92; Vandecasteele, J. P. et al., Methods Enzymol., 1982, 89: 484-490). The enzymatic conversion reaction from 6-aminocaproic acid to adipic acid, which consists of the same number of carbons as 6-aminocaproic acid, is highly valued as a novel technology as well as for its high commercial value. However, an enzyme or a microorganism that can participate in the actual reaction is not known.
In this regard, the inventors of the present disclosure isolated a novel microorganism having deamination activity while studying the deamination of 6-aminocaproic acid, and accordingly, a novel enzyme has been discovered from the novel microorganism, thereby completing the present disclosure.